FSHB rs121908071: Understanding This Rare Genetic Variant
The rs121908071 variant is a rare genetic alteration located within the FSHB gene. It is associated with isolated follicle-stimulating hormone (FSH) deficiency, which can impact reproductive development and fertility in both males and females.
What each genotype means
Typical FSH subunit function
You carry two copies of the common, functional FSHB sequence at this position. This genotype is associated with normal synthesis of the follicle-stimulating hormone beta subunit and standard reproductive endocrine function. It does not confer an elevated risk for isolated gonadotropin deficiency.
Carried by more than 99.99% of individuals across all major global ancestries.
Carrier of FSH deficiency variant
You carry one functional allele and one loss-of-function allele in the FSHB gene. Research indicates that heterozygous carriers generally maintain normal reproductive development, puberty, and fertility, though slightly reduced circulating FSH levels have been observed in animal models. Carriers have a 50% chance of passing this variant to biological offspring.
Extremely rare globally, identified in fewer than 1 in 10,000 individuals across populations in gnomAD.
Isolated FSH deficiency risk
You carry two copies of the loss-of-function variant in the FSHB gene. Published clinical literature strongly links biallelic loss of FSHB to congenital isolated follicle-stimulating hormone deficiency (hypogonadotropic hypogonadism 24), which presents as primary amenorrhea and incomplete sexual maturation in females, or azoospermia and small testes in males. This report is an informational genetic summary and does not establish a clinical diagnosis.
Extremely rare worldwide, typically documented only in individual case reports or consanguineous pedigrees.
What is the rs121908071 Variant?
The rs121908071 variant is a specific change in the DNA sequence of the FSHB gene. In genetics, a variant like this represents a difference in the nucleotide sequence compared to the most common version found in the human population. This particular variant is categorized as a loss-of-function mutation, meaning it disrupts the normal instructions the gene provides to the body. Because the FSHB gene is responsible for creating a critical component of a reproductive hormone, changes here can have significant biological consequences. This variant is located on chromosome 11, where the FSHB gene resides. It is considered extremely rare, appearing at a very low frequency in global population databases. Understanding such variants helps researchers map the complex relationship between our genetic code and the hormonal systems that regulate human development and reproductive health.
The Role of the FSHB Gene
The FSHB gene provides the blueprint for the beta-subunit of follicle-stimulating hormone (FSH). FSH is a vital glycoprotein hormone produced by the pituitary gland. In the body, FSH works in tandem with other hormones to regulate the reproductive system. In females, it is essential for the maturation of ovarian follicles and the regulation of the menstrual cycle. In males, it plays a key role in spermatogenesis, the process by which sperm cells are produced. Because the beta-subunit is unique to FSH, it determines the hormone's specific biological activity. When the FSHB gene is functioning correctly, the body produces enough FSH to support normal puberty, fertility, and reproductive function. If the gene is altered, as seen with certain pathogenic variants, the production of functional FSH can be severely impaired, leading to hormonal imbalances that affect these critical biological processes.
Research and Clinical Associations
Scientific research has linked pathogenic variants in the FSHB gene to a condition known as isolated follicle-stimulating hormone deficiency. This condition is characterized by low levels of FSH, while other pituitary hormones often remain within normal ranges. In clinical reports, individuals with these variants have presented with primary amenorrhea (the absence of menstruation) and delayed puberty in females, or azoospermia (the absence of sperm in the ejaculate) in males. The evidence for this association is derived from case studies and clinical observations of individuals with specific mutations. While the link between loss-of-function variants in FSHB and these reproductive challenges is well-documented in medical literature, the overall prevalence of such cases is very low. It is important to note that this information is for educational purposes; individuals concerned about reproductive health or hormonal symptoms should consult with an endocrinologist or a qualified healthcare provider for personalized evaluation and guidance.
Population Frequency and Interpretation
The rs121908071 variant is classified as ultra-rare in global populations, with a minor allele frequency (MAF) reported in databases like gnomAD as less than 0.00005. This extreme rarity means that the vast majority of the human population does not carry this specific variant. Because it is so uncommon, it is not typically included in standard, broad-spectrum genetic screening panels. When a variant is this rare, its presence is often identified only through targeted clinical sequencing in individuals who are already experiencing specific symptoms of hormonal deficiency. The rarity of the variant underscores that it is not a common cause of reproductive issues in the general population. For those who may have received information about this variant through genetic testing, it is essential to discuss the findings with a genetic counselor or physician who can interpret the results within the context of an individual's specific clinical history and symptoms.
How common is this variant?
The rs121908071 variant is ultra-rare in global populations, with a minor allele frequency (MAF) of less than 0.00005 in gnomAD.
Frequently asked questions
What is isolated FSH deficiency?
Isolated FSH deficiency is a rare condition where the body does not produce enough follicle-stimulating hormone, while other pituitary hormones remain normal. This can lead to delayed puberty, infertility, or primary amenorrhea.
Is rs121908071 a common cause of infertility?
No, this variant is extremely rare and is not a common cause of infertility in the general population. Most cases of infertility are caused by a wide variety of other factors.
How is this variant inherited?
Conditions associated with loss-of-function mutations in the FSHB gene are typically inherited in an autosomal recessive manner. This means an individual usually needs to inherit two copies of the variant to manifest the clinical condition.
Should I be tested for this variant?
Genetic testing for specific rare variants is generally only recommended by clinicians if there is a strong clinical suspicion of a specific genetic disorder. You should discuss any concerns about your reproductive health with a doctor.
Sources & further reading
Educational information only, last refreshed 10/13/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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Promoter-adjacent variant linked to FSHB expression, influencing basal follicle-stimulating hormone levels, menstrual cycle duration, and twinning propensity.
Functional promoter variant in FSHB influencing serum FSH concentrations and reproductive lifespan.
Variant in the promoter region of FSHB associated with circulating follicle-stimulating hormone levels, age at menarche, and reproductive lifespan.
Located in the promoter of FSHB (c.-211G>T), this variant downregulates follicle-stimulating hormone transcription and is strongly associated with male infertility traits (oligozoospermia) and altered female reproductive lifespan.
Variant in the promoter region of FSHB associated with altered follicle-stimulating hormone levels, timing of menarche, and female reproductive lifespan.
Functional variant in FSHB causing congenital isolated follicle-stimulating hormone deficiency.